Purpose: In ¹²³I-ioflupane single-photon emission computerized tomography, anatomical landmarks are often indistinct, making identification of the anterior commissure–posterior commissure (AC–PC) line difficult in clinical practice. This study evaluated the usefulness of the tuberculum sellae–occipital protuberance (TS–OP) line and the nasion–fourth ventricle (nasion–4V) line, which is routinely used at our institution, as alternative reference lines. Methods: Angular differences from the AC–PC line were calculated, and inter-observer reproducibility and agreement of each line were assessed using the ICC and Bland–Altman analysis. In addition, ΔSBR (specific binding ratio) was calculated using our institutional reference axis to investigate the effect of angular differences on quantitative values. Results: The largest angular difference from the AC–PC line was observed for the nasion–4V line (−2.5°), although no significant differences were found among the lines. All lines demonstrated good reproducibility; however, the TS–EOP line showed slightly lower agreement, likely due to differences in recognition of bony morphology. Bland–Altman analysis revealed that the nasion–4V line had the smallest bias, and the TS–IOP line also showed a small bias of less than 1°. Although the nasion–4V line exhibited a relatively larger angular difference, it maintained high reproducibility and agreement. An angular difference of approximately 2.5° resulted in a maximum SBR change of 0.15. Conclusion: The nasion–4V line demonstrated high reproducibility and agreement, while the TS–IOP line showed minimal deviation and can be defined using bony landmarks. Both may be considered alternative reference lines when the AC–PC line is difficult to identify, with the TS–IOP line potentially representing a more stable option.

Purpose: This study aimed to determine the discrepancy between planned and actual source positions in the Geneva applicator for cervical cancer brachy therapy and to evaluate its impact on dose distribution. Methods: The Geneva applicator was placed on a computed tomography (CT) couch top, and CT images were acquired at each source dwell position to determine the actual source locations. The discrepancy between the actual source positions and the planned source positions reconstructed using the applicator modeling (AM) method was calculated. These discrepancies were then incorporated into the treatment plans of 13 patients who underwent brachytherapy for cervical cancer at our institution. Dose metrics, including D_90% for the high-risk clinical target volume (HR-CTV) and D_2cc for the bladder, rectum, small bowel, and large bowel, were evaluated between the original and the modified treatment plans. Results: The overall three-dimensional displacement of the source was 0.86±0.15 mm. Regarding dose metrics, the D_90% for the HR-CTV was significantly higher (mean increase, 1.38%) in the plans reflecting the actual source positions, while the D_2cc for the bladder and rectum was significantly lower (mean decrease, 2.29% and 2.57%, respectively) compared to the original plans. Conclusion: The results suggest that incorporating actual source positions into treatment planning can improve the accuracy of applicator reconstruction in cervical cancer brachytherapy.

Purpose: This study aimed to evaluate metal artifacts in cardiac magnetic resonance imaging using four pacing leads and four defibrillation leads and to clarify the effects of lead differences on image quality. Methods: Each lead was fixed in a phantom and aligned parallel to the X-, Y-, and Z-axis. Short-axis images were acquired using balanced steady-state free precession (balanced SSFP) and fast gradient echo (FGRE). Artifact area (S₀) and increase rate (ΔS) were calculated. For each lead, the maximum value among the three axes was used to perform inter-lead comparisons. Visual assessment was also performed using short-axis images. Results: In the physical evaluation, both S₀ and ΔS tended to be greater with FGRE than with balanced SSFP for all leads. The median (range) of the maximum S₀ and ΔS values among the three axes for each lead were 152.02 mm² (119.17–183.49) and 5024.27% (4562.10–6956.83), respectively, for pacing leads, and 114.43 mm² (79.51–148.11) and 2073.16% (1398.30–3561.46), respectively, for defibrillation leads. In the visual assessment, metal artifacts were significantly larger in some defibrillation leads in both balanced SSFP and FGRE. Conclusion: Pacing leads showed relatively small inter-lead differences, whereas some defibrillation leads exhibited inter-lead variability, suggesting the involvement of structural factors.

Purpose: This study aimed to evaluate the impact of increasing the number of automatic field-in-field (FIF) subfields per tangential beam on dose distribution and delivery efficiency in tangential whole-breast irradiation. Methods: Ten women with left-sided early breast cancer treated under deep inspiratory breath-hold were retrospectively selected, and tangential whole-breast irradiation plans were generated using the RayStation treatment planning system. Beam arrangement and dose normalization conditions were kept identical, while only the number of Auto FIF subfields per beam was varied from 0 to 4 (FIF0–FIF4). To ensure coverage of the evaluation clinical target volume (CTV_eval), dose was normalized to an open tangential plan. Evaluated dosimetric parameters were CTV_eval, homogeneity index (HI), body maximum dose and D_1cc, absolute V_40Gy of the left lung, and total monitor units (MUs). Pairwise comparisons between adjacent FIF levels were performed using Wilcoxon’s signed-rank tests. Results: CTV_eval dose remained stable for all FIF settings. HI improved stepwise from FIF0 through FIF3, with no further significant improvement at FIF4. The body maximum dose decreased significantly from FIF0 to FIF1, and body D_1cc showed significant improvement up to FIF2. Absolute left lung V_40Gy decreased markedly from FIF0 to FIF1. Total MUs increased monotonically with each additional subfield, with significant stepwise increases through FIF3 but no further significant increase at FIF4. Conclusion: Increasing the number of Auto FIF subfields improved whole-breast dose homogeneity, but using more than three subfields per beam yielded minimal additional dosimetric benefit while increasing MU. A setting of approximately two to three Auto FIF subfields per beam appears to offer a reasonable balance between plan quality and delivery efficiency.

Purpose: We evaluated the ability of an MJP X-ray cut filter (hereafter referred to as “cut filter”) to reduce fluoroscopic dose rate and assessed its impact on image quality in pediatric angiography. Methods: Fundamental assessments included fluoroscopic dose rate measurements, spectral analysis, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and visual evaluation were conducted. Body thickness was also measured in 412 pediatric patients aged 10 years or younger. Image visibility was visually assessed using a paired-comparison method. Results: The use of a cut filter reduced the fluoroscopic dose rate by 15%–25%. Spectral analysis confirmed that the low-energy component was effectively reduced via use of a cut filter. Changes in SNR ranged from −1.7% to +3.0%. CNR decreased by 27% when polymethyl methacrylate (PMMA) thickness was 20 cm. Visual assessment showed an average degree of preference of 0.119 at a PMMA thickness of 20 cm. Respective average body thicknesses at 0 and 10 years of age were 10.5±0.63 and 17.0±2.04 cm, respectively. Conclusion: An MJP X-ray cut filter can reduce fluoroscopic dose rate while maintaining sufficient image visibility in pediatric angiography, particularly for patients with a body thickness of 15 cm or less.